Brush knob



Jan. 2, 1951 G. RUDAT ET AL BRUSH KNOB Filed Oct. 15, 1948 555.2 95 flu 12 5i C'ZzarZss E- I BE Patented Jan. 2, 1951 BRUSH KNOB George Rudat and Charles B. Lee, Racine, Wis.,

assignors to John Oster Manufacturing Company, Racine, Wis., a corporation of Wisconsin Application October 15, 1948, Serial No. 54,622

2 Claims. 1

This invention relates to electric motors and refers more particularly to brush knobs of the type which close the outer or anti-commutator ends of brush holder tubes in such motors.

Electric motors are commonly provided with metal brush holder tubes which are mounted on the motor frame in some appropriate manner and in which the brushes are axially slidable. To hold the brush in constant engagement with the commutator an insulative knob is secured to the anti-commutator end of the brush holder tube to close the same and a compression spring in the brush holder tube reacts between this knob and the brush.

The brush knob normally projects to the outside of the motor frame or housing so that it may be readily removed from the brush holder tube to permit access to the brush for repair or replacement, and it will therefore be immediately apparent that the knob must be made of insulative material to preclude short circuiting of the brushes. On the other hand it is extremely desirable that the knob have an electrically conductive insert which will firmly engage the outer end of the brush holder tube and against which the brush spring will react, to thereby conduct current from the brush holder tube to the brush spring and thence to the brush. Such an insert is necessary because the sliding contact between the sides of the brush and the inner surface of the tube provides an inadequate and undependable path for current flow; and because of the relatively small size of the insert it should be permanently secured in the brush knob to preclude its loss when work is done on the brushes.

Heretofore inserts of this type have been molded into the brush holder knob, which is usually made of phenolic or similar plastic material, but it will be readily seen that this is a relatively expensive procedure and entails numerous complications in the molding operation.

It is therefore an object of this invention to provide a brush knob of the character described having a metallic insert capable of conducting current from the brush holder tube to the brush spring and in which such insert, although not embedded in the knob during molding, is nevertheless permanently secured in position in the knob.

Another object of this invention resides in the provision of a brush knob insert of the character described which may be formed as a simple and inexpensive stamping and which may be readily] manently seated therein in one simple and rapid operation involving no expensive or unusual tools. v

Another object of this invention resides in the provision of a method of inserting a conductive brush knob insert into an insulative brush knob and permanently seating the same therein.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it, being understood that such changes in the precise em bodiment of the herein disclosed invention may be made as come within the scope of the claims. The accompanying drawing illustrates one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view partly in cross section/and partly in end elevation showing an electric-motor provided with brush knobs having inserts made in-accordance with this invention; Figure 2 shows the brush knob and insert of this invention in longitudinal section, together with the tool used in seating the insert, shown in side elevation, all being shown in properrelative position for assembly;

Figure 3 is a view similar to Figure 2 but with the insert in position in the brush knob preliminary to its securement therein;

Figure 4 is a view similar to Figure 3 but showing the insert seated, with the tool about to be withdrawn; and

Figure 5 is a group perspective view of the brush knob and insert of this invention i position for assembly. 7

Referring now more particularly to the accompanying drawing, in which like numerals indicate like parts throughout the'several views, the numeral 5 designates generally-an end bell comprising part of the housing or casing of an electric motor having a commutator 6 engaged by opposite conductive brushes 1. The brushes are held in metal brush holder tubes 8, in which they are axially slidable and from which they project for engagement with the commutator, and the brush holder tubes are retained in position on the end bell of the motor housing by suitable insulative mounting-s 9. Current is supplied to the tubes, and thus to the brushes therein, by means of a conductor l0 connected to each of the tubes.

1 9M or anti-commutator end of each e ,er o fi i e d A a .sin cathi's ,cavity is smaller: in diameter than the brush holder tube is externally threaded, as at H, and said end of the tube is closed by an insulative brush knob l2 having a threaded well I3 to enable it to be screwed in place over the threaded end of the tube 8. A compression spring l4 reacts between the knob and the brush I to maintain the brush constantly engaged with the commutator Eachlbrushsknob:projects slightly beyond the exterior of the motor housing, through a suitable port IS in the housing, so as to expose a screw ce-t e, knob'may be readily screwed off the end of the tube to permit access to the springsll and brush driver slot [6 in its head for access.

1 without necessitating disassembly' of -:the motor housing.

At the bottom of the well ,l3 in v the lknob,.isthe.

insert ll of this invention which, in its final assembled form, is a circular, dished metallic ::;ele-..

ment having its concavesurface facing the mouth -tof, the well. ,lt will be.seen that.as tltabrush knob l is screwedllintofplace .on -the brush-holder "tube the end of the tube" is brought into firm eneasement With thelinargihalaedge; pontion-o flthe fin'seiift lfl he oiiter end oflthei com- 1p p seat's tagainstlthe insertthe presence lofgtheiinsertiin thelirio insures thata .gqgd conductive path will bevrl rovided between time we e-t h-t. v

- i -b ui e ke' l m d? nat eu ee mnne we i i e l z or eeiielme d e s-thread 1 e n rmed a 1111 same i cel nd w edin Jfo hefu'll depth 0 hewell: At the sa-me time Phebdfivme th -Wel a d -a ne u t ra the junction f iiiejfsic w pfg th cavity and ithebott'omwalllof thewell I The inseitgfllisiniti 1y formed asladisk l e e i e eh e we: h in a d am.- e iii il l ee h e iei ided eme e or 9; t i 'q fl We s-1 ijl t e ai-t m edge punc ibut havni end, is inserted axially into the A well: andpressed F 'eei st heetqerex, ade-ei-i e s m n ilttwill as s?! t at h n ifli 'en lp e su e sbmu h toibear upon the stampin it will flipzov r-fl i- 1 it will reverse its:purvat e so that its outermost fulcrums on the annular edge' or shoulder I9 e ie e (Peri her ita m i t b t o q nee eu dea e adjac nt t d 's Thus when the tool is withdrawnethestamping will be found lto be seated in the bottom-of the threaded well -with ;,its rear convex surface en- ,gagin the shq ulder f 9 a protruding; intothe .relie't cavity; is, Qbviously the relief cavity must be provided in the knob in order to enable the stamping to flip over, and while the shape of the cavity and the location of the annular edge or shoulder l9 may be varied from that shown they should always be such that the disk will be restrained from taking too great a, curvature.

From the foregoing description, taken together with .thejaccompanying drawing it will be .readily apparentthatthis invention provides an inexpensive brush knob of the character described, and a practical method of providing the same with a metallic insert that will preclude the necessity for molding such inserts into the brush :knob -and,will atthe same time provide an en- "tirelysatisfactory insert which is permanently seated inithe .brush knob and which may be intherewith-thewell -being threaded toreceive the threaded end of a metal brush-holder-tube, the junction between the bore andthe' bottomof the threaded well providing can .Iann'ular shoulder spaced radially in from the sicleof the threaded Well; :and a unitarydished metal disk non-removably wedged inthe bottomof'rthe threaded: well byvhaving its 1 convex side bearing-. 011 the annular shoulder and rprotrluding into. the l relief cavity and its: periphery bearing against the side of the threaded well near the bottom thereof.

GEORGE :R'UDAT; CHARL' ESBJLEEJ-f REFERENQESwGI T-ED The following references [are of record in the file of this patent:

STATES PATENTS Number Name Date 1,507,840 Landgraf \1. Sept- 9, 1924 1,801,006 Jacoby Apr. .14, .1931 2,032;084=- Dunham Feb..25, 1936 2,045,293. Carlson June23-, 1936 2,039,678 Wiemers g Aug..-10,'3-1 937 "2,264,998 Miner- Deo-.' 2,1-1"941 2,313,228 Domonkos I Mar. 9, 1943 FOREIGN PATENTS Number Country. Date; 1

Great Britain Jan. 16; 1930 

